This invention relates to a variable displacement vane type hydraulic pump, and deals more particularly with such a pump of a simple, inexpensive and reliable construction wherein the displacement of the pump is automatically regulated in response to the output or delivery pressure and wherein for a given application the pump may be so designed that the delivery pressure remains substantially constant throughout a range of delivery rates extending from zero flow to the maximum flow required by the application.
The pump of this invention is particularly well adapted for use in pressurizing gasoline or other liquid fuel in conjunction with a fuel injection system for an internal combustion engine, but its use is not limited to such application and it instead may be used in many other applications to which its characteristics lend themselves.
Prior U.S. Pat. No. 2,635,551; U.S. Pat. No. 2,678,607; U.S. Pat. No. 2,775,946; U.S. Pat. No. 3,070,020; U.S. Pat. No. 3,743,445; and U.S. Pat. No. 3,924,970 show variable displacement vane type pumps each having a laterally shifting flow modulating member for varying the pump displacement. However, in each case the flow modulating member is of relatively large size and surrounds the rotor, making a relatively complex overall construction and, among other things, creating sealing problems.
In contrast to the patents mentioned above, the pump of this invention uses a rotor having a central cylindrical recess receiving a cylindrical cam portion of a flow modulating member with a fluid confining or pumping chamber being defined between the outer surface of the cam portion and the inwardly facing cylindrical surface of the rotor recess. Only a few simple seals are therefore required to prevent leakage from the pump while nevertheless permitting rotation of the rotor relative to its housing.